The invention relates to a method for the manufacture of a guide blade for a turbine or compressor guide wheel, through the use of a profiled bar of heat and corrosion resistant metal that is cut to an oversize length, in particular in preparation for soldering into the guide wheel, as well as a guide blade manufactured according to the method.
Guide blades for a turbine guide wheel are known that are formed with a profiled base. It is known that the guide blade with said base is inserted in a compatibly profile-shaped groove in the blade carrier and that the outer ring, the so-called covering rim of the guide wheel, is riveted on. To this end, the guide blade is formed at the head end with a pin provided for riveting.
Another known manufacture of a vane ring and one often applied in the present state of the art consists in that the guide blades are joined by butt soldering at the base end and at the head end, respectively, to the inner and outer vane ring, respectively. Through use of, for example, gold-nickel solder 80 Au/20 Ni, high-strength soldered joints able to withstand high stress are soldered under protective gas or in vacuum, which are eminently suitable for stresses under permanent operating temperatures of up to 400.degree. C. In the case of higher operating temperatures, for example, a palladium-nickel solder 60 Pd/40 Ni melting at a temperature about 300.degree. C. higher is advantageously used. The mechanical properties of the soldered joints obtained with these solders are about 20% below the ultimate stress values of the material of the parts to be soldered.
With regard to the required strength, especially given the stresses arising in the vane ring due to different thermal expansions, the soldered joint constitutes the weakest link of a chain of ultimate stress values. In addition, during butt soldering of a guide blade standing essentially vertically on the base, the soldered joint is under critically high stress, due to concentration of the magnetic flux in the edge area of the blade contour, in the nature of a notch effect.